At the thoracic level, which muscle group is expected to retain function?

At the thoracic level, which muscle group is expected to retain function?

• A. Abdominals
• B. Biceps
• C. Gastrocnemius
• D. Deltoid

Answer: (A)

The main idea is that which muscles stay functional hinges on the level of the spinal lesion and the nerve roots that supply them. At a thoracic level, the abdominal muscles are innervated by thoracic nerve roots (roughly T6–T12). Those nerves can remain functionally intact enough to provide trunk control, even when other muscle groups are weakened by the thoracic-level injury. The arms (biceps and deltoid) come from cervical nerves (C5–C6), and the gastrocnemius comes from sacral nerves (S1–S2); in a thoracic-level lesion, these latter groups are typically more affected or less reliably preserved for practical function, whereas the abdominal musculature often retains measurable activity. So, the abdominals are the muscle group most likely to retain function at thoracic spinal levels, providing essential trunk stability and assist with respiration and posture.